1. Field of the Invention
The present invention relates to a method of manufacturing a thermally insulating sash bar.
2. Prior Art
Japan Patent Laid-Open Publication (Kokai) No. 54-119739 discloses a method of manufacturing a thermally insulating sash bar. As shown in FIGS. 1a to 1g, the prior method comprises: (a) providing an elongated hollow metallic sash bar A including a pair of spaced interior and exterior outer members 1,2 connected by a pair of first and second inner members 3,4 so as to define between the outer members 1,2 a longitudinally extending hollow chamber 5 and a pair of longitudinally extending first and second channels 6,7 (FIG. 1a); (b) forming a longitudinal dinal gap 9 in and along the first inner member 3 by use of a cutter 8 (FIG. 1b); (c) covering the longitudinal gap in the first inner member 3 with a thermally insulating strip 10 (FIG. 1c); (d) then introducing a mass of thermally insulating synthetic resin into and curing the same within the first channel 6 to fill the latter with the cured thermally insulating synthetic resin 11 (FIG. 1d); (e) then forming a longitudinal gap 12 in and along the second inner member 4 by use of a cutter 8 (FIG. 1e); (f) covering the longitudinal gap 12 in the second inner member 4 with a thermally insulating strip 10 (FIG. 1f); and (g) then introducing a mass of the thermally insulating synthetic resin into and curing the same within the second channel 7 to fill the latter with the cured thermally insulating synthetic resin 11 (FIG. 1g).
Thus, the longitudinal gaps 9,12 in the first and second inner members 3,4 are formed at absolutely separate stages of process, i.e. the steps (b) and (e) above. This requires two separate cutting stations in the assembly line, making the assembly line complicated and costly. Yet, if there is only one cutting station in the assembly line, it is necessary to bring the sash bar A back to such one and the same cutting station for the step (e) (after the first channel 6 has been filled with the cured thermally insulating synthetic resin 11), which is very time-consuming.